Moss potentially could face a four-game suspension without pay by the NFL if it is established through his alleged connection to Anthony Galea, a Toronto-based physician, that he used HGH or otherwise violated the league's policy on banned performance-enhancing substances.

But while the NFL prohibits use of HGH, the league does not test players for it because a reliable urine test has not been developed and because the NFL Players Association has not agreed to the league's proposal to blood-test players. That leaves the NFL relying on investigations by law enforcement agencies to provide the information by which the league can try to catch and punish players who improperly obtain or use HGH.

Two people with knowledge of the investigation of Galea, speaking on condition of anonymity because the probe is ongoing, said Thursday that Moss was among the professional athletes treated by the doctor. One said Moss was the player that Galea's medical assistant, Mary Anne Catalano, was on her way to meet in Washington when she was arrested at the U.S.-Canada border on Sept. 14, 2009, with HGH, syringes and other medical equipment in her vehicle.

Moss declined to discuss the case Wednesday at Redskins Park, before his potential involvement in it was reported. Redskins Coach Mike Shanahan told reporters following a speaking engagement Thursday that "just because someone is associated with a doctor does not mean a person is guilty." Shanahan said the Redskins are "going to let the due process take care of itself."

The Buffalo News first reported that Moss was among those treated by Galea. The newspaper said that federal prosecutors at this point do not plan to file criminal charges against Moss or any other athlete linked to the doctor.

The case prompted a renewed call for the NFL to enact blood-testing of players for HGH, which is thought to promote recovery from injuries.

"My views have been consistent throughout: The NFL, the NBA, Major League Baseball and the NHL ought to be doing blood-testing for HGH," Gary Wadler, a drug-testing expert and the chairman of the prohibited list and methods subcommittee for the World Anti-Doping Agency, said in a telephone interview. "To wait for a urine test to be developed -- they may be waiting for many years, if it's developed at all. This [blood] test has been around. It's validated."

An NFL spokesman said the league had no further comment Thursday about the Galea investigation. The league issued a written statement Tuesday in which it said that "this case highlights the need for enhanced testing and in our discussions about a new collective bargaining agreement with the NFL Players Association, we have proposed expanding our current testing program to include growth hormone."

The players' union expressed a willingness in recent months to discuss the blood-testing proposal. The union previously had a long-standing opposition to allowing players to be blood-tested, contending that players would be tested for HGH only when a reliable urine test for it was developed.

"I don't think a blood test would be justified," Mark Bruener, a tight end who played 14 seasons for the Pittsburgh Steelers and Houston Texans between 1995 and 2008 and a former member of union's ruling executive committee, said by telephone Thursday. "That's extremely invasive on an athlete. We have one of the most aggressive, productive drug-testing policies in all of sports. To go to that extreme [with blood-testing], I'm not sure that's good for the health of an athlete."

The league currently conducts urine tests of players for steroids and other items on a lengthy list of banned substances.

The union declined to comment Thursday, a spokesman said.

League officials previously said they believe that blood-testing for HGH has progressed to the point at which such a test should be included in the NFL's program. The league has proposed such a test as part of the current labor negotiations with the union, and league officials previously left open the possibility of blood-testing for HGH being put into effect as part of a separate agreement between the sides even before a new labor deal could be completed.

But two people familiar with the issue said this week that there has been little to no movement in the discussions between the league and the union on the matter. One person familiar with the deliberations said the discussions will continue but it is not clear at this point when such a test might be put into effect.

"The NFL and all of these leagues, they have tended to be reactive to adverse publicity and circumstances and then they make incremental changes to their program," Wadler said. "Clearly the policy in the NFL is better than it used to be. But there should be more than incremental changes. . . . I would hope the issue of HGH is dealt with in a clear and transparent way during this round of collective bargaining in the NFL."

A professional rugby player in Britain was suspended in February for testing positive for HGH use, a development that drug-testing experts cited as proof that the blood test is effective.

On Tuesday, U.S. federal authorities charged Galea with unlawfully treating athletes with HGH and the unapproved drug Actovegin. According to court documents, two current NFL players and one former NFL player received medical treatment from Galea and the former player admitted to purchasing HGH kits from Galea. The two current NFL players said they did not knowingly use HGH, according to the documents. The players were not identified by name in court documents.

The NFL suspended New England Patriots safety Rodney Harrison for four games and Dallas Cowboys quarterbacks coach Wade Wilson for five games in 2007 after they were initially linked to banned substances through a criminal investigation. The NFL's written statement Tuesday said that "when we have had evidence of illegal purchase, possession, or use of HGH, we have imposed discipline and are fully prepared to do so again if the facts support it."

What remains uncertain is how prevalent HGH use is among NFL players. Former Redskins offensive tackle Jon Jansen told HBO in 2006 that "maybe 15, 20 percent" of NFL players used performance-enhancing drugs and use was "on the rise" because of undetected HGH use. Other estimates have varied.

"I have no idea, really," Bruener said Thursday. "I know I have never been in any conversations in any circles that have been involved with it. My belief is, it's not widespread in the NFL. I don't know if that's a skewed opinion or not."